Prior generation fluoroquinolones predominantly either inhibit topoisomerase II (DNA Gyrase) or topoisomerase IV and therefore only require one genetic mutation for bacteria to develop resistance. Fourth-generation fluoroquinolones are equally effective against topoisomerase II and IV, which significantly expands their spectrum of action against gram-positive agents and atypical mycobacteria and Nocardia . This duality of action of the fourth generation fluoroquinolones requires that for bacteria to become resistant to these agents, the bacteria must undergo two genetic mutations resulting in a significantly decreased chance of an organism developing resistance.Minimum inhibitory concentrations determined in vitro suggest that fourth-generation fluoroquinolones are more effective than second- and third-generation fluoroquinolones against gram-positive bacteria including Staphylococcal species found in endophthalmitis and bacterial keratitis cultures. The increased efficacy of fourth-generation fluoroquinolones make these antibiotics important agents to evaluate for prophylaxis against post-PRK infections. This was a retrospective chart review.